In a conventional wire bonding pad structure of a semiconductor device, bonding pads are directly in contact with a top metal interconnect. For example, U.S. Pat. No. 6,560,862 to Chen et al. discloses a method for fabricating a bonding pad structure. The method disclosed by Chen et al. provides a substrate having a top metal layer and a passivation layer overlying the top metal layer, etching the passivation layer within a metal via area to form a trench exposing at least a portion of the top metal layer, and forming a patterned, extended bonding pad over the etched passivation layer and lining the trench. In another example, U.S. Pat. No. 6,376,353, Zhou et al. discloses a method for fabricating wire bond pads on pure copper damascene. The Zhou et al. patent describes processes is which a special Al—Cu bond layer or region is placed on the top of the underlying copper pad metal.
FIG. 1 illustrates a cross-sectional view of semiconductor device with a bonding pad according to a conventional fabrication method. As shown in FIG. 1, a first insulating layer 12 is deposited on a semiconductor substrate 10 with at least a predetermined structure and some part of the first insulating layer 12 is removed through an etching process to form a trench. The trench is filled with a metal material to form a top metal interconnect 14. Here, the top metal interconnect 14 is generally formed of copper.
Then, a second insulating layer 16 is deposited over the substrate 10 including the top metal interconnect 14. Some part of the second insulating layer 16 is removed through photolithography and etching processes using a mask for the formation of a pad. As a result, the top portion of the top metal interconnect 14 is exposed.
Next, a metal layer is formed over the resulting substrate 10 including the second insulating layer 16. Some parts of the metal layer are removed by means of photolithography and etching processes using a mask for the formation of a metal pad (not shown). As a result, the metal pad 18 is formed on the top metal interconnect 14. Here, the top metal interconnect is directly in contact with the metal pad 18. A passivation layer 20 is deposited over the resulting substrate 10 and some part of the passivation layer 20 is removed by means of photolithography and etching processes using the mask for the formation of a pad. Thus, the top portion of the metal pad 18 is exposed through the passivation layer 20.
However, the conventional bonding pad structure described above, the copper interconnect is in direct contact with the bonding pad, which may deteriorate reliability during a wire bonding process to wire bonding pads or reliability tests such as PCT (pressure cooker test) and TC (temperature cycling).